Carburetor for liquid fuels



May 1933- B. M. DODDS CARBURETOR FOR LIQUID FUELS Filed March 30, 1931INVI/VTaR Patented May 2, 1933 UNITED. STATES,

EDWIN .MAI'HIESON DODDS, F WATFORD, ENGLAND cannnnn'ron roa LIQUIDApplication filed March 30, 1931, Serial No. 526,153, and in GreatBritain June 11, 1930.'

This invention relates to carburetors for liquid fuels, and refers moreparticularly to carburetors designed for use with internal combustionengines, and it has'for its object to provide improved means toproportionately retard the delivery of fuel to form the high speedmixtureas the speed increases.

According to the present invention, supplementary air is supplied atsuch a point i with respect tothepoint' of issuance of the fuel from'the jet, that when the vacuum within the choke or induction tube changesas a result of changes'in engine conditions, the consequent change inthe rate of flow of the supplementary air will act to control the rateof flow of the fuel from the jet, in such a manner that the fuel-airratio may thereby be maintained constant for all engine conditions andpositions of the throttle,,or,-the

device may be set to give either a progressive increaseior decreaseinfuel-air ratio with increasing choke vacuum. p

According to one form of :the, invention, a tube is provided for thesupply of the supplementary air, saidtube'being so arranged as to admitthe said air at a point adjacent the discharge orifice of the jet.Provision is preferably made for initially adjusting the size of the airoutlet to the tube. The arrangement is such thatthe direction of flow ofthe incoming air is more or less opposed to that of the fuel as itissues from thejet.

In the arrangement referred tothe air inlet tube is so arranged andconstructed that its inner endmore or less shrouds the exit for the fuelfrom the jet. Provision may be made whereby the position of the shroudmay be adjusted with respect to the end of the jet. p 1 .y In order thatthe invention maybethe better understood, reference-is had to theappended drawinginwhichz- Fig. 1 is a front elevation of. one'formcarburetor according to the present invenion. I Fig. 2 is a sideelevation. I Fig. 3 is a plan.

Fig. 2.

Fig. 4 is a sectional elevation on line A A Fig. 5 is a sectional viewalong line BB,

Fig. 3. V

Fig. 6 is a plan of a carburetor embodying a modification.

1 Fig. 7 is a section online CC Fig. 6. Fig; 8 is a'section on line DD'of Fig.6. F 1g. 9 is a fragmentary view showing a.

further modification. I p

" Fig. 10 is avertical se'ction'on line -EE,

Fig. 9. j Fig. 11 is a sectional plan on line F- -F,

Fig. 12 is a sectional view showing a modified detail of construction. 7

Fig. 18 isaplan. v 6 Fig. 14'isa sectional view showing a furthermodified detail. Figs. 15 ,and 16 are views showing modified forms ofjets and supplementary air supply ducts'arranged in accordance with thepress ent invention. I

' Referring to Figs. 1 to 5 of the drawing,

1 indicates the choke or induction tube of the carburetor, and 2 thethrottle valve which is operated in the usual manner by means of a. 7

control member attached to the lever 3, any suitable form of float, notshown, and disposed within the float chamber 4, being 'provided.

Located within the choketubeis a fuel jet 5, which is at its lower endscrewed into the tube 6, which is formed integral with the choke tube,and into which tube the fuelflows from the float chamber by wayof a tube7 formed integral with the said float chamber, and connected to the tube6 by means of a hollow bolt 8 through which the fuel also passes I inits passage to the tube 6. c

Formed upon the choke tube at a point diametrically opposite to thepoint at which the tube 6 is formed is a boss, 9 into which is screwthreaded a tube 10, the lower end of-which extends into the-choke tubeand is disposed in closeproximity to the exit end of the jet 5 orshrouds the same, according to the manner in which the said tube 10 isadjusted, the bore of this latter tube at its lower end being coned, andof a slightly larger diameter. than the outer diameter of the upper endof I the said jet. m0

" ing the tube in the manner just described,

the low pressure within the choketube 1,

out a small controllable range as-comparedto body may be screwedinwardly to cause its inner extremity to enter the bore of the tube 10to the desired extent to thereby adjust the rate of flow of air downthistube,-a milled lock nut being provided for locking the body 13=initsadjusted position;

From the foregoing, it will be readily seen a that the" tube 10 may beadjusted vertically with respect to the fuel. jet by screwing the tubeup or downthe boss 9. In order tolock the tube 10 in its adjustedposition a milled locknutlc; is provided thereon. By adjustit ispossible to also adjustt-he fuel-air ratio of the mixture.

The action of the carburetor during the normal running of the engine issuch that in additionto-causingifuel' to be drawnfrom the jet 5 in theusual manner, also causes a stream of air to be drawn in through thetube 10,-tlie rate of flow of'which stream of air increases when thepressure within the choke tube drops as a result of a change of enginecondition, the'result of this being that the pressure immediatelyaround'the point at which the fuel leaves the jet variesthroughthe widerrange of pressure variation within the choke tube for various engineconditions.

This fornr of construction provides the in cident al advantage that byreason of the sup- T plementa-ry air and petrol streams flowing in fromdiametrically opposite points of the choke tube and along the same axisor diamet er, a very complete atomization of the fuel takes place. 1

For the purpose of permitting of the idling of the engine when thethrottle is closed, a b e-pass duct 17; is formed within a lateralextension 18 cast along one side of the choke tube,- the said ductcommunicating at one end with that portion of the choke tube designed tobelocated between the engine intake manifold and the throttle valve 2,by means of a port 1 9, and at the other end. communicating withtheportion of the choke tube adjacent the jet by means of a port 20, Figs.3 ,4a-nd-5,

Screwed within the port 20 and extending to within close proximity tothe jet 5 is'a nozzle 21 ,which is so arranged as to be capable ofadjustment toward and away from the jet, a suitable lock nut 22 beingprovided to lock the nozzle in its adjusted position, the arrangementbeing such that when the throttle is closed a slow running charge isdrawn into the nozzle, through the duct 17, port 19, into the forwardend of the choke tube and then into the engine.

Fromthe foregoing, it will be readily seen that by adjusting thedistance of the nozzle 21' from the jet 5, control of the slow running fuel air ratio *is'efiectedi- For the purpose of effecting the adjustmentof the speed of slow running, an adjusting screw 23 is provided, whichis of such length as to permit of its inner end being screwed intotheduct and thus in effect restricting its bore, a lock nut 23 being. pro--vided-t-o lockthis:adjustingscrew in the desired position.

According to the form of constructionshown iii-Figs. 6, 7 and 8, insteadof the choke tube being provided with a bypass-,such above descrlbed, anauxiliary choke o-r- 1nduction tube 2% isprovided, the inner endof whichis in communication with that part ofthe choke tube 1 which is on" theengine side of the throttle valve 2.

The choke tube 2 1 is-provided with a fuel jet and supplementary airsupply tube constructed and arranged in a similar manner tothat'withint-he main choke tube and indicated by corresponding referencenumerals, this choke tube, jet andsupplementary air'supply tube,however, being of somewhat smaller dimensionsthan the main choke tube,jet and supplementary air supply tube re spect-ively, the fuel for thisjet beingfed from the float chamber by way of awtubeQ-a This auxiliarychoketube is provided with abolt 24 whereby the speed of slow runningmay be coiitrolled,-a lock nut 2 L being provided for locking thesaidbolt in its adjusted position:

According to the modification shown in F 9, 10 and 11' instead of anauxiliary jet or by-pass being provided, the main jet and su'iplementary air supply tube, instead of being arranged so that theircommon axis intercepts the longitudinal axis of the choke tube 1, arearranged at one side of the said longitudinal axis and in closerproximity to the throttle valve 2, which is provided with a small tube26, which extends through the throttle valve, and when the latter isclosed the outer end of this the becomes located in close proximity tothe jet, and thus permits of a sufficient supply of mixture to be drawninto the engine to permit of its idling when the said valve iscl'osed.

For the purpose of permitting the tube 26 to be initially adjusted, thistube is provided with a screw thread, as shown in Figs. 10 and 11, whichengages with a corresponding thread within the valve 2. j i

From the foregoing it will be readily unders'tood that adjustment of{the 1 body 13 causes an adjustment of the petrol-air ratio of thenormal running :mixture, while adjustment of the distance of the tube 26from the jet controls the slow running fuel-air ratio. i v

The slow running devices illustrated in Figs. 1 and 9 dispense withthenecessity for a fine bore pilot jet with its well known tendency tochoke up, It must be under stood, however, that the st scheme describedin this specification can be used with any of the ordinary types ofpil'otjet. i

According to a further modification shown in Figs. 12 and 13, the hollowboss upon the upper end of the tube together withthe body 13 isdispensed with, and screwed uponthc upper end of the tube 10 is a hollowperforated body 27, mounted by means ofascrew 28 within the upperportion ofwhich body is an aneroid barometer disc 29' carrying upon itsunderside a needle valve 30 designed to coact with the air entry orificeat the upper end of the tube, the arrangement being such as toautomatically reduce the amount of air entering the tube as thecarburetor is moved to higher altitudes, and thus cause the mixture-tobecome richer;

The arrangement shown in Fig. 14 is do signed to automatically cause themixture to mewetrer 1i so a f c (it beco ll witl ncrease f lt tud ,a1l

around'the underside of an air inlet orifice 33 formed within a boss 34which at its lower end connects the body 27 to thetube 10.

These latter arrangements are particularly advantageous when thecarburetor is used upon air-craft en gines,as they dispense with thenecessity of employing a manually operated air bleed valve or body suchas 13, previously described. i In Figs. 15 to 18 are shown alternativeconstructions and arrangements of jetsand supplementary air supplytubes.

If desired, the invention may be applied to carluiretors havingsubmerged I For fuel testing work,-for which the carburetor is found tobe particularly suited,

the jet or jets, as the case may be may be supplied from constant level"fuel cups,' one or other of which can be connected to the et or jets bymeans of a suitable'two way cock or similar device, the various controlsand ad-' justable parts being suitably marked or call brated to permitofcomparative tests'to be readily made between two kinds of fuel.

Although in the particular forms of the invention above described thejets and supplementary air supply tubeshave been arranged with theirlongitudinal axes disposed at right angles with'respect to the longitu-'dinal axes of the choke tubes, it is not desired to limit the inventionto this arrange-c orjcts, as the case may be, can bemoderated tothusya-ry the fuel-ratio as best suits: the circumstance or conditionsof running, such means preferablyalso functioning automatically bybeing, for instance connected to the throttle control lever;

' I claim: 1

1. A" carburetor including z'an air intake pipe; a throttle valve withinsaid pipe; a jet within said pipe; a liquidfuel supply for said jet; asupplementary 'imp'erforate air supply tube communicating with the outeratmosphere, extending over and shrouding the outlet end of the'je't andleaving an annular space between it and'said jet; means for adjustingtheair supply through said tube; a bye-passhaving one end locatedadacent the jet and the other in the intake pipe "at a point upon theengine side of said throttle valve, whereby the slow running of theengine is permitted upon the closing of said throttle valve, i 1 2. Acarburetor including; an air intake pipe; a throttle valve Withinsaidpipe; a jet within said pipe; a liquid fuel supply for said jet; asupplementary imperforate air supply tube communicating with the outeratmosphere extending over and shrouding the outletend of the jet andleaving an annular space between it and'said jet; means for adjustingthe air supply through said tube; a bye-pass around said throttle valveto permit of the slow'running'of the engine when said throttle isclosed; a nozzle at one end of saidbye-pass disposed adjacent thejet;

and means for adjusting theposition of said nozzle'with respect to'saidjet.

3. A carburetor. including: an air intake pipe; a throttle valve withinsaid pipe; a jet within said pipe; a liquid fuel supply forsaid jet; asupplementary imperforate air supply: tube communicating with the outeratmosphere, extending over and shrouding the outlet end of the jet andleaving an annular space between itand said jet; means for adjusting theair supply through said tube; a bye-pass around said throttle'valve topermit of the slow running of the engine when said throttle'is closed; anozzle at one end zle" with respect to said jet; means for regulatingthe amount of fuel air mixture pass,- ingthroughsaid bye-pass.

f. A carburetor including an air intake pipe; a throttle valve withinsaid pipe; a jet within said pipe; a liquid fuel supply for said jet; asupplementary imperforate air supply tube communicating with the outeratmosphere, extending over and shrouding the outlet end of the jet andleaving an annular space between it and said jet; and means whereby theslow running of theengine is permitted upon the closing of the saidthrottle valve comprising a second air intake pipe connected to theengine side of the throttle valve; a jet within said pipe; a liquidfuelsu-pply for said jet; a supplementary imperforate air supply tubeCO1I1- municating with the outer atmosphere, extending over andshrouding the outlet end of the jet and leaving an annular space betweenit and said j ct.

5. An improved carburetor for internal combustion engines, consisting inthe combination of an air intake pipe; a jet within said pipe; a liquidfuel supply for said jet, means for providing an air supply toproportionately retard the delivery of fuel to form the high speedmixture as: the speed increases, comprising a supplementary air supplytube the wall of Which is imper-forate, said tube communicating withtheouter atmosphere, extending over and shroudi-ng the outlet end of thejet and leaving an annular space between it and said jet so as toreverse the direction of flow of all of the fuel as it issues from saidjet; together with means whereby' the amount of air admitted throughsaid tube may be adjusted.

6. An improved carburetor for internal combustion engines, consisting inthe combination of an air intake pipe; a jet within said pipe a liquidfuel supply for said jet; means for providing an air sup-ply toproportionately retard the delivery of fuel to form the high speedmixture as the speed increases, comprising a supplementary air supplytube the wall of which is imperforate, said tube communicating with theouter atmosphere, extending over and shrouding the outlet end of the jetand. leaving an annular space between it and said jet so. as to reversethe direction of flow of all of the fuel leaving said j et, said tubealso being so. arranged that the flow of air passing theretl'irough isopposed in direction to. the fuel flowing tlirouglisaid jet togetherwith means where by the amount of air admitted through said tube may beadjusted.

'Z'. An improved carburetor for internal combustion engines, consistingin the combination of an air intake pipe; a ct within said pipe a liquidfuel supply for said jet; means forproviding an airsupply-toproportionate- 1y retard the delivery of" fuel toform the high speedmixture as the speed increases, comprising a supplementary air supplytube the wall of which is imperforate, said tube communicating with theouter atmosphere, extending over and shrouding the outlet end of the jetand leaving an annular space be tween it and said jet so as to reversethe direction of flow of all of the fuel as it issues from said jet;means whereby the amount of air admitted through said tube may beadjusted; and means whereby the position of the end of the said tubewith respect to the discharge end of said jet may be initially adjusted.

8. An improved carburetor for internal combustion engines, consisting inthe combination of an air intake pipe; a throttle valve within saidpipe; a jet within said pipe; a liquid fuel supply for said jet; meansfor peviding an air supply to proportionately retard the delivery offuel to form the high speed mixture as the speed increases, comprising asupplen'ientary air supply tube the wall of which is imperforate, saidtube commi'micating with the outer atmosphere, eX- tending over andshrouding the outlet end of the jet and leaving an annular space betweenit and said jet so as to reverse the direction of flow of all of thefuel as it issues from said jet; means whereby the amount of airadmitted through said tube may be adjusted; means whereby the positionof the end of the said tube with respect to the discharge end of saidjet may be adjusted; and means whereby the slow running of the engine ispermitted upon the closing of said throttle valve.

,9 An improved carburetor for internal combustion engines, consisting inthe combination of an air intake pipe; a throttle valve within saidpipe; a jet within said pipe; :1 liquid fuel supply for said jet; meansfor providing an air supply to proportionately retard the delivery offuel to form the high speed mixture as the speed increases; comprising asupplementary air supply tube the wall of which is imperforate, saidtube communicating with the outer atmosphere extending over andshrouding the outlet end of the jet and leaving an annular space betweenit and said jet so as to reverse the direction of flow of all of thefuel as it issues from said jet; means for adjusting the air supplythrough said tube; a by-pass having one end located adjacent the jet andthe other in the intake pipe at a point upon the en'- gine side of saidthrottle valve, whereby the slow running of the engine is permitted uponthe closing of said throttle valve, comprising a tube extending throughsaid throt tlevalve.

10. An improved carburetor for internal combustion. engines, consistingin the combination of' an air intake pipe; a throttle valve withinsaidpipe; a jet within said pipe; a liquidfuel supply for said jet;

means for providing an air supply to proportionately retard the deliveryof fuel to form the high speed mixture as the speed increases,comprising a supplementary airsupply tube the wall, of which isimperforate, said tube communicating with the outer atmosphere,extending over and shrouding the outlet end of the jet and leaving anannular space between it and said jet so as to reverse the direction offlow of all of the fuel as it issues from said jet; meansfor adjustingthe air supply through said tube; a'by-pass having one end locatedadjacent the jet and'the other in the intake pipe at a point upon theengine side of said throttle valve, whereby the slow running oftheengine is permitted upon the closing of said throttle valve, comprisinga tube extending through'said throttle valve, and adjustable towards andaway from the jet.

11.An improved carburetor for internal combustion engines, consisting inthe com bination of an air intake pipe; a jet Within said pipe; a liquidfuel supply forsaid jet; means for providing an air supply toproportionately retard the delivery of fuel to form the high speedmixture as the speed increases, comprising a supplementary imperforateair supply tube communicating with the outer atmosphere, extending overand shrouding the outletend of the jet and leaving an annular spacebetween it'and said jet so as to reverse the direction of flow of all ofthe fuel as it issues from said jet; together with means actuated bydifferences of barometric pressure whereby theamount of air admittedthrough said tube is automatically adjusted.

In testimony whereof I afiix my signaturer EDWIN MATHIESON DODDS.

